By means of electron assisted hot filament chemical vapour depositiontechnology, nanocrystalline diamond films are deposited on polishedn-(100)Si wafer surface at 1 kPa gas pressure. The deposited films arecharacterized with a Raman spectrometer, atomic force microscope,semiconductor characterization system and Hall effect measurementsystem. The results show that, when bias current is larger than 2 A,sheet hole concentration can increase to a value greater than1013 cm−2 and undoped nanocrystalline diamond films with ap-type semiconducting characteristic form. Heterojunction between n-Sisubstrate and the nanocrystalline diamond films deposited with 2 A and6 A bias current has an evident junction effect. Hole formationmechanisms in the films are discussed.